The Ozone Shield Unit 2: The Atmosphere

What is it? Ozone layer – area in the atmosphere where ozone is highly concentrated Absorbs most of the UV light from the sun UV radiation damages genetic material in living cells (acts like a sunscreen) Made up of three Oxygen atoms When is radiation good?

Chlorofluorocarbons (CFCs) Miracle chemicals Nonpoisonous, non flammable, do not corrode metals Used as coolants in refrigerators and air conditioners Also as a “fizz” for making plastics foams and a propellant in aerosol cans Stable at Earth’s surface, but are not so in the atmosphere and breakdown Ozone (1970s – shocking) Single chlorine atom can destroy as many as 100,000 ozone molecules! (more on this later)

The Ozone Hole In 1985, an article in Nature reported the ozone layer had thinned by 50-98%! During the winter (very cold temperatures), chlorine is separated from CFCs on the surface of a special type of high-altitude clouds When the temperature warms in the spring UV radiation splits chlorine which begins to destroy ozone Satellites had observed this as early as 1978

Why does it look like it’s not getting any bigger?

Effects on/of Living Things So if ozone is an air pollutant, why can’t we just produce more? Less ozone means more UV radiation – lather on the sunscreen! Can kill phytoplankton on the surface of the ocean Disrupts the food chain – why? Increased carbon dioxide Amphibians that lay eggs in shallow water also especially susceptible (and “good” indicators)

Protecting the Ozone Layer Montreal protocol – countries around the world agreed to limit their production of CFCs U.S. pledged to ban all substances by 2000 International success story – kind of CFCs last a very long time (60-120 years) Developing countries are actually increasing their production of them